User post: HELP!! Please I need your advice!! Should I let her have him?

Let me start by warning you, my story is complicated, but I hope you can help me!

I have been dating the same guy for the past three years. At times it has been exclusively, at others casual, and well there have been those times where we have completely stopped talking. In these 3 years we also have both dated other people. His other relationships have been more controversial than mine but we both have had our share of dating others, but we always end up back with eachother. It has been three years of the same rollercoaster and with New Year's around the corner I'm ready to stop this ride, or so I wish I could be.

I met him about three years ago at a family event, he was a sweet guy and a lot of fun to talk to. We began flirting, and then talking on the phone every night, then we began going places, and one thing led to another and what do you know, it's been three years!!! He is one of the sweetest guys I have ever met, when we are together there is nothing I would rather be doing. He is caring, attentive, honest, funny, loving, and affectionate. It's been so long and he still makes my knees shake when he touches me, and my heart skip a beat when he kisses me. So why isn't he my boyfriend you might be asking yourself, let me tell you why. A couple of months ago, I told him how I felt about him and he told me he was not ready to committ to a relationship (his previous relationship from before I was even around really hurt him and left him with trust issues), I decided to back off, give him some space and give myself a break from all this chaos. He decided to start dating someone else. Recently, I ran into him and the girl he's talking to, and it felt like there was a huge hole in my stomach!! Later that same day I confronted him about him seeing someone else when he had just told me he wasn't ready to commit to something with me, and in that process we began, well we picked up right where we left off.

So at the moment, he is back on the ride with me and still seeing her. It was so hard for me to admit to myself that ok, maybe I am a little in love with him, and now that I have, it seems like it doesn't even matter because he doesn't know what he wants. He tells me he would love to try something serious with me, and that he cares so much about me, and that he would hate for us to not be able to be friends in the long-run, and that I'm special to him, but then he's talking to someone else! What's his deal!! I get that he's scared of being hurt but so am I! I have been so honest with him, and he knows what I want from him but he doesn't do anything. I just want him to say something like "ok, let's give it a try" or "Sorry, I want her" or something, ANYTHING!!

I'm in love with him, and I don't want to let him go, but trying to figure out where we stand half of the time seems worse. I know that it is also my fault because I have allowed it to continue for so long, because everytime he comes back I drop everything and let him in, but I don't want to continue feeling confused, and I don't want to hurt when I see him with someone else. What do you guys think I should do? Should I stick around and keep trying to show him that I won't hurt him, that I really do care and love him? Should I back off and let the other girl have him? Should I just let him go?

PLEASE TELL ME WHAT YOU THINK!!
please, I need someone else's perspective because mine is killing me!!